SPIT electrical mechanics delivered a drive system for an hydraulic test bench for a Japanese Manufacturer of hydraulic motors. The system was engineered to deliver maximum power and availability at the lowest operating costs.

The system consist of two asynchronous ABB high efficiency motors; one of 400 kW @ 1000 rpm used as a brake generator and one of 250 kW @ 1500 rpm for the pump motor. Both machines are driven by ABB ACS800-107 inverter modules. The inverter modules are coupled via a common DC busbar. The grid-connection is made via a Regenerative IGBT supply unit of 440 kVA.

SPIT was the main contractor for electrical engineering, panelbuilding and software engineering and commissioning of the drive system.

ABB’s industrial multidrive series, the ACS800, can be used in virtually any test bench applications, including chassis dynamometers, engine test stands, and transmission tests. The drives series features proprietary open-loop Direct Torque Control technology that eliminates the need for installing encoders and enables the drives to calculate the state (torque and flux) of the motor, making the motor controllers trip-less. The absence of a required encoder can also reduce capital costs by up to 25 percent, when compared to flux vector PWM (Pulse-Width-Modulated) drives.

“Because this open-loop control of speed or torque is so precise, the drives can adapt to and handle changes in load immediately,” according to Jan Kleinjan, Project Manager for SPIT electrical mechanics. The ability to provide full torque at zero motor speed, as well as high-operating torque at low speeds, enables the drives to respond immediately and precisely to load changes as they vary.

A DTC flux optimisation feature automatically adapts the motor flux to the load, so that the ACS800 drive provides only the amount of power needed. When the motor is not fully loaded, this increases energy savings quickly. A half percent increase in efficiency of a 500 kW motor can save more than 23.000 kWh per year, alone, according to Kleinjan.